package ppx_python
[@@deriving] plugin to generate Python conversion functions
Install
Dune Dependency
Authors
Maintainers
Sources
ppx_python-v0.15.0.tar.gz
sha256=471f4d2bffb46e540ee59c1d8f1f7fb0285f8e4a3bece3e875fe040ffb2fc415
doc/src/ppx_python_conv/ppx_python_conv.ml.html
Source file ppx_python_conv.ml
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open Base open Ppxlib open Ast_builder.Default let default = Attribute.declare "python.default" Attribute.Context.label_declaration Ast_pattern.(pstr (pstr_eval __ nil ^:: nil)) (fun x -> x) ;; let option = Attribute.declare "python.option" Attribute.Context.label_declaration Ast_pattern.(pstr nil) (fun x -> x) ;; let disallow_extra_fields = Attribute.declare "python.disallow_extra_fields" Attribute.Context.type_declaration Ast_pattern.(pstr nil) () ;; let lident ~loc str = Loc.make ~loc (Lident str) let fresh_label = let counter = ref 0 in fun ~loc -> Int.incr counter; let label = Printf.sprintf "_lbl_%d" !counter in ppat_var (Loc.make ~loc label) ~loc, pexp_ident (lident ~loc label) ~loc ;; let raise_errorf ~loc fmt = Location.raise_errorf ~loc (Stdlib.( ^^ ) "ppx_python: " fmt) (* Generated function names. *) let python_of tname = "python_of_" ^ tname let of_python tname = tname ^ "_of_python" (* For parameterized types, use these function names as arguments. *) let python_of_arg tname = "__python_of_" ^ tname let of_python_arg tname = "__" ^ tname ^ "_of_python" let app_list ~loc (func : expression) (args : expression list) = [%expr [%e func] [%e elist ~loc args]] ;; let curry_app_list ~loc (func : expression) (args : expression list) = List.fold_left args ~init:func ~f:(fun acc arg -> [%expr [%e acc] [%e arg]]) ;; let fun_multi ~loc (args : label list) (body : expression) = List.fold_right args ~init:body ~f:(fun arg acc -> pexp_fun Nolabel ~loc None (ppat_var (Loc.make ~loc arg) ~loc) acc) ;; let closure_of_fn (fn : expression -> expression) ~loc : expression = let loc = { loc with loc_ghost = true } in let arg_pat, arg_expr = fresh_label ~loc in pexp_fun Nolabel ~loc None arg_pat (fn arg_expr) ;; module Signature : sig val gen : [ `to_ | `of_ | `both ] -> (signature, rec_flag * type_declaration list) Deriving.Generator.t end = struct let of_td ~kind td : signature_item list = let { Location.loc; txt = tname } = td.ptype_name in let to_python_type = List.fold_left (List.rev td.ptype_params) ~init: [%type: [%t Ppxlib.core_type_of_type_declaration td] -> Pytypes.pyobject] ~f:(fun acc (tvar, _variance) -> [%type: ([%t tvar] -> Pytypes.pyobject) -> [%t acc]]) in let of_python_type = List.fold_left (List.rev td.ptype_params) ~init: [%type: Pytypes.pyobject -> [%t Ppxlib.core_type_of_type_declaration td]] ~f:(fun acc (tvar, _variance) -> [%type: (Pytypes.pyobject -> [%t tvar]) -> [%t acc]]) in let psig_value ~name ~type_ = psig_value ~loc (value_description ~loc ~name:(Loc.make name ~loc) ~type_ ~prim:[]) in match kind with | `both -> [ psig_value ~name:(python_of tname) ~type_:to_python_type ; psig_value ~name:(of_python tname) ~type_:of_python_type ] | `to_ -> [ psig_value ~name:(python_of tname) ~type_:to_python_type ] | `of_ -> [ psig_value ~name:(of_python tname) ~type_:of_python_type ] ;; let gen kind = Deriving.Generator.make_noarg (fun ~loc:_ ~path:_ (_rec_flag, tds) -> List.concat_map tds ~f:(of_td ~kind)) ;; end module Structure : sig val of_python_ty : core_type -> expression -> expression val to_python_ty : core_type -> expression -> expression val gen : [ `to_ | `of_ | `both ] -> (structure, rec_flag * type_declaration list) Deriving.Generator.t end = struct let change_lidloc_suffix ~f lid = Located.map (function | Lident str -> Lident (f str) | Ldot (m, str) -> Ldot (m, f str) | Lapply _ -> raise_errorf ~loc:lid.loc "lapply not supported") lid ;; let rec handle_core_type ~tuple ~var ~constr ~polymorphic_variant ct v = let loc = { ct.ptyp_loc with loc_ghost = true } in match ct.ptyp_desc with | Ptyp_tuple core_types -> tuple ~loc core_types v | Ptyp_var tv -> [%expr [%e pexp_ident ~loc (lident (var tv) ~loc)] [%e v]] | Ptyp_constr (longident_loc, args) -> let lid_loc = change_lidloc_suffix ~f:constr longident_loc in let args = List.map args ~f:(fun arg -> let arg_fn = handle_core_type ~tuple ~var ~constr ~polymorphic_variant arg in closure_of_fn ~loc arg_fn) @ [ v ] in curry_app_list (pexp_ident lid_loc ~loc) args ~loc | Ptyp_alias (alias, _) -> handle_core_type ~tuple ~var ~constr ~polymorphic_variant alias v | Ptyp_variant (row_fields, Closed, None) -> polymorphic_variant row_fields ~loc v | Ptyp_variant (_, _, _) -> raise_errorf ~loc "'%a' not supported, only closed variants with no labels are supported" Pprintast.core_type ct | _ -> raise_errorf ~loc "'%a' not supported" Pprintast.core_type ct ;; let rec of_python_ty core_type v = handle_core_type ~tuple:(of_python_tuple ~wrap:Fn.id) ~var:of_python_arg ~constr:of_python ~polymorphic_variant:of_python_polymorphic_variant core_type v and of_python_tuple ~wrap ~loc core_types v = let list = List.mapi core_types ~f:(fun i core_type -> [%expr let t = Py.Tuple.get_item [%e v] [%e eint i ~loc] in [%e of_python_ty core_type [%expr t]]]) in let tuple_len = eint (List.length core_types) ~loc in [%expr if not (Py.Tuple.check [%e v]) then Printf.sprintf "not a python tuple %s" (Py.Object.to_string [%e v]) |> failwith; let p_len = Py.Tuple.size [%e v] in if p_len <> [%e tuple_len] then Printf.sprintf "tuple size mismatch %d <> %d" [%e tuple_len] p_len |> failwith; [%e wrap (pexp_tuple ~loc list)]] and of_python_polymorphic_variant row_fields ~loc v = let match_cases ~args = List.map row_fields ~f:(fun { prf_desc; prf_loc = loc; prf_attributes = _ } -> match prf_desc with | Rinherit _ -> raise_errorf ~loc "inherited polymorphic variant not supported" | Rtag (label, has_constant_constructor, ctors) -> let rhs args = pexp_variant ~loc label.txt args in let rhs = match ctors, has_constant_constructor with | [], _ -> rhs None | [ core_type ], false -> rhs (Some (of_python_ty core_type args)) | [ _ ], true -> raise_errorf ~loc "cannot have both a constant and non-constant constructor" | _, _ -> raise_errorf ~loc "multiple constructors are not supported" in case ~lhs:(ppat_constant ~loc (Pconst_string (label.txt, loc, None))) ~guard:None ~rhs) @ [ case ~lhs:[%pat? cstor] ~guard:None ~rhs:[%expr failwith (Printf.sprintf "unexpected constructor %s" cstor)] ] in [%expr if not (Py.Tuple.check [%e v]) then Printf.sprintf "not a python tuple %s" (Py.Object.to_string [%e v]) |> failwith; let p_len = Py.Tuple.size [%e v] in if p_len <> 2 then Printf.sprintf "not a python pair %s" (Py.Object.to_string [%e v]) |> failwith; let cstor, _args = Py.Tuple.to_pair [%e v] in let cstor = Py.String.to_string cstor in [%e pexp_match ~loc [%expr cstor] (match_cases ~args:[%expr _args])]] ;; let of_python_fields fields ~wrap ~loc ~allow_extra_fields v = let record_fields = List.map fields ~f:(fun field -> let name_as_string = estring ~loc field.pld_name.txt in let default_branch = match Attribute.get default field with | Some default -> default | None -> (match Attribute.get option field with | Some _ -> [%expr None] | None -> [%expr Printf.sprintf "cannot find field %s in dict" [%e name_as_string] |> failwith]) in let expr = [%expr match Ppx_python_runtime.Dict_str_keys.find [%e v] [%e name_as_string] with | exception (Stdlib.Not_found | Not_found_s _) -> [%e default_branch] | v -> __pyocaml_field_read := !__pyocaml_field_read + 1; [%e of_python_ty field.pld_type [%expr v]]] in lident field.pld_name.txt ~loc, expr) in let check_extra_fields = if allow_extra_fields then [%expr ()] else ( (* The [fail_on_extra_fields] bit is slow but this is ok as it's only used when an error is generated so outside of the path that we're optimizing for. *) let field_names = List.map fields ~f:(fun field -> estring ~loc field.pld_name.txt) |> elist ~loc in [%expr if !__pyocaml_field_read <> Py.Dict.size [%e v] then Ppx_python_runtime.Dict_str_keys.fail_on_extra_fields [%e v] ~expected_field_names:[%e field_names]]) in [%expr if not (Py.Dict.check [%e v]) then Printf.sprintf "not a python dict %s" (Py.Object.to_string [%e v]) |> failwith; let __pyocaml_field_read = ref 0 in let __pyocaml_res = [%e wrap (pexp_record record_fields ~loc None)] in [%e check_extra_fields]; __pyocaml_res] ;; let of_python_variant variant ~loc ~allow_extra_fields v = let match_cases ~args = List.map variant ~f:(fun variant -> let rhs args = pexp_construct ~loc (lident ~loc variant.pcd_name.txt) args in let rhs = match variant.pcd_args with | Pcstr_tuple [] -> rhs None | Pcstr_tuple core_types -> of_python_tuple core_types args ~loc ~wrap:(fun v -> rhs (Some v)) | Pcstr_record fields -> of_python_fields fields ~loc args ~wrap:(fun record -> rhs (Some record)) ~allow_extra_fields in case ~lhs:(ppat_constant ~loc (Pconst_string (variant.pcd_name.txt, loc, None))) ~guard:None ~rhs) @ [ case ~lhs:[%pat? cstor] ~guard:None ~rhs:[%expr failwith (Printf.sprintf "unexpected constructor %s" cstor)] ] in [%expr if not (Py.Tuple.check [%e v]) then Printf.sprintf "not a python tuple %s" (Py.Object.to_string [%e v]) |> failwith; let p_len = Py.Tuple.size [%e v] in if p_len <> 2 then Printf.sprintf "not a python pair %s" (Py.Object.to_string [%e v]) |> failwith; let cstor, _args = Py.Tuple.to_pair [%e v] in let cstor = Py.String.to_string cstor in [%e pexp_match ~loc [%expr cstor] (match_cases ~args:[%expr _args])]] ;; let rec to_python_ty core_type v = let tuple ~loc core_types v = let pat, expr = to_python_tuple ~loc core_types in pexp_let ~loc Nonrecursive [ value_binding ~loc ~pat ~expr:v ] expr in handle_core_type ~tuple ~var:python_of_arg ~constr:python_of ~polymorphic_variant:to_polymorphic_variant core_type v and to_python_tuple ~loc core_types = let var_name i = "t" ^ Int.to_string i in let pat = List.mapi core_types ~f:(fun i _ -> ppat_var ~loc (Loc.make (var_name i) ~loc)) |> ppat_tuple ~loc in let list = List.mapi core_types ~f:(fun i core_type -> to_python_ty core_type (pexp_ident (lident (var_name i) ~loc) ~loc)) in pat, app_list [%expr Py.Tuple.of_list] ~loc list and to_polymorphic_variant row_fields ~loc v = let match_cases = List.map row_fields ~f:(fun { prf_desc; prf_loc = loc; prf_attributes = _ } -> match prf_desc with | Rinherit _ -> raise_errorf ~loc "inherited polymorphic variant not supported" | Rtag (label, has_constant_constructor, ctors) -> let constructor = estring ~loc label.txt in let args_lhs, args_rhs = match ctors, has_constant_constructor with | [], _ -> None, [%expr Py.none] | [ core_type ], false -> Some [%pat? t], to_python_ty core_type [%expr t] | [ _ ], true -> raise_errorf ~loc "cannot have both a constant and non-constant constructor" | _, _ -> raise_errorf ~loc "multiple constructors are not supported" in case ~lhs:(ppat_variant ~loc label.txt args_lhs) ~guard:None ~rhs: [%expr Py.Tuple.of_pair (Py.String.of_string [%e constructor], [%e args_rhs])]) in pexp_match ~loc v match_cases ;; let to_python_fields fields ~loc v = let mandatory_fields, optional_fields = List.partition_tf fields ~f:(fun field -> Attribute.get option field |> Option.is_none) in let mandatory_fields = List.map mandatory_fields ~f:(fun field -> let name_as_string = estring ~loc field.pld_name.txt in let value = pexp_field v (lident ~loc field.pld_name.txt) ~loc in [%expr [%e name_as_string], [%e to_python_ty field.pld_type value]]) in let mandatory_dict = app_list ~loc [%expr Ppx_python_runtime.Dict_str_keys.create] mandatory_fields in if List.is_empty optional_fields then mandatory_dict else ( let optional_setters = List.map optional_fields ~f:(fun field -> let name_as_string = estring ~loc field.pld_name.txt in let value = pexp_field v (lident ~loc field.pld_name.txt) ~loc in let pat_ident = lident ~loc "pat_value" |> pexp_ident ~loc in [%expr match [%e value] with | None -> () | Some _ as pat_value -> Ppx_python_runtime.Dict_str_keys.set dict [%e name_as_string] [%e to_python_ty field.pld_type pat_ident]]) in [%expr let dict = [%e mandatory_dict] in [%e esequence ~loc optional_setters]; dict]) ;; let to_python_variant variant ~loc v = let match_cases = List.map variant ~f:(fun variant -> let constructor = estring ~loc variant.pcd_name.txt in let args_lhs, args_rhs = match variant.pcd_args with | Pcstr_tuple [] -> None, [%expr Py.none] | Pcstr_tuple core_types -> let pat, expr = to_python_tuple ~loc core_types in Some pat, expr | Pcstr_record fields -> Some [%pat? t], to_python_fields fields ~loc [%expr t] in case ~lhs:(ppat_construct ~loc (lident ~loc variant.pcd_name.txt) args_lhs) ~guard:None ~rhs: [%expr Py.Tuple.of_pair (Py.String.of_string [%e constructor], [%e args_rhs])]) in pexp_match ~loc v match_cases ;; let expr_of_td ~tvar_wrapper ~type_expr ~variant ~record td = let { Location.loc; txt = _ } = td.ptype_name in let tvars = List.map td.ptype_params ~f:(fun (te, _variance) -> match te.ptyp_desc with | Ptyp_var lbl -> tvar_wrapper lbl | _ -> (* we've called [name_type_params_in_td] *) assert false) in let expr arg_t = match td.ptype_kind with | Ptype_abstract -> (match td.ptype_manifest with | None -> raise_errorf ~loc "abstract types not yet supported" | Some ty -> type_expr ty arg_t) | Ptype_variant cstrs -> variant cstrs ~loc arg_t | Ptype_record fields -> record fields ~loc arg_t | Ptype_open -> raise_errorf ~loc "open types not yet supported" in fun_multi ~loc tvars (closure_of_fn expr ~loc) ;; let gen kind = let attributes = match kind with | `both | `of_ -> [ Attribute.T default; Attribute.T option; Attribute.T disallow_extra_fields ] | `to_ -> [] in Deriving.Generator.make_noarg ~attributes (fun ~loc ~path:_ (rec_flag, tds) -> let tds = List.map tds ~f:name_type_params_in_td in let of_python_bindings () = List.map tds ~f:(fun td -> let pat = let { Location.loc; txt = tname } = td.ptype_name in let name = of_python tname in ppat_var ~loc (Loc.make name ~loc) in let expr = let allow_extra_fields = Option.is_none (Attribute.get disallow_extra_fields td) in expr_of_td ~tvar_wrapper:of_python_arg ~type_expr:of_python_ty ~variant:(of_python_variant ~allow_extra_fields) ~record:(of_python_fields ~wrap:Fn.id ~allow_extra_fields) td in value_binding ~loc ~pat ~expr) in let to_python_bindings () = List.map tds ~f:(fun td -> let pat = let { Location.loc; txt = tname } = td.ptype_name in let name = python_of tname in ppat_var ~loc (Loc.make name ~loc) in let expr = expr_of_td ~tvar_wrapper:python_of_arg ~type_expr:to_python_ty ~variant:to_python_variant ~record:to_python_fields td in value_binding ~loc ~pat ~expr) in let bindings = match kind with | `both -> to_python_bindings () @ of_python_bindings () | `to_ -> to_python_bindings () | `of_ -> of_python_bindings () in [ pstr_value ~loc (really_recursive rec_flag tds) bindings ]) ;; end let python = Deriving.add "python" ~str_type_decl:(Structure.gen `both) ~sig_type_decl:(Signature.gen `both) ;; module Python_of = struct let name = "python_of" let extension ~loc ~path:_ ctyp = closure_of_fn (Structure.to_python_ty ctyp) ~loc let deriver = Deriving.add name ~str_type_decl:(Structure.gen `to_) ~sig_type_decl:(Signature.gen `to_) ~extension ;; end module Of_python = struct let name = "of_python" let extension ~loc ~path:_ ctyp = closure_of_fn (Structure.of_python_ty ctyp) ~loc let deriver = Deriving.add name ~str_type_decl:(Structure.gen `of_) ~sig_type_decl:(Signature.gen `of_) ~extension ;; end
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